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Sunita Williams faces power outage in space home
Seema Hakhu Kachru in Houston | February 13, 2007 15:13 IST
Indian American astronaut Sunita Williams along with two other colleagues experienced a power outage aboard the International Space Station knocking out communications with Earth.
The glitch took place on Sunday but all systems were restored within a day, NASA officials at the Johnson Space Center in Houston said.
On Sunday, a power channel in the station's Port 4 (P4) solar array electrical system shut down due to a glitch with an electrical distribution device known as a direct current switching unit, the officials said.
"The station's three crew members were not in any danger, but it did turn an off-duty day into a full work shift," the space agency said in a statement.
The power drop led to a temporary loss of ISS communications and the shutdown of heating units, some science equipment and one of three operating US gyroscopes used for attitude control.
NASA officials said it took about 31 hours for flight controllers and the space station's Expedition 14 crew to restore ISS systems to normal.
"I wanted to congratulate you on a really well done job," Expedition 14 commander Michael Lopez-Alegria told flight controllers in a message re-broadcast on NASA TV after power was restored.
The ISS did fly in a two-gyroscope mode for attitude control, the minimum required to orient the station without consuming propellant for Russian thrusters, during the glitch.
"One gyroscope that helps control the station's orientation went offline for a while but eventually came back up. Several heaters used for thermal balance of external station components were affected but have since resumed normal operations," the officials said.
Expedition 14 continues preparations for a February 22 spacewalk. Commander Mike Lopez-Alegria and Flight Engineer Mikhail Tyurin will don Russian Orlan space suits.
Among other activities, they will ready a Progress 23 cargo capsule for undocking. The Progress 23 antenna did not retract properly when it docked in October 2006.
NASA engineers are still pondering over the source of a day-long power loss aboard the ISS that resulted in shut down of the science and communications equipment.